1. Field of the Invention
This invention relates a method for producing a single crystalline member, and more particularly a method for producing a single crystalline member preferably usable for a semiconductor- and an oxide-single crystalline substrate.
2. Description of the Prior Art
Single crystalline substrates made of semiconductor materials or oxide materials are used for devices such as a silicon integrated circuit, an optical device, an electronic device and a solar battery.
These substrates have been produced as follows: Large single crystals made of semiconductor material or oxide material are grown by a crystal pulling method (Czochralski method), a horizontal/vertical Bridgman method or a floating zone-melting method, and thereafter, are cut out to given sizes by a mechanical method using a crystal-cutting machine, etc.
Moreover, in employing the thus obtained single crystalline substrate for an electronic/optical device, its surface should be mirror-polished.
However, as the diameter of the single crystal become large, a machine to cut it also become large and complex. Moreover, the single crystal itself is required to have a mechanical strength to endure the above cutting process, so that it is required to have a large thickness. Thus, the above conventional method does not enable the single crystal to have sufficient utilizing efficiency for the device fabrication.
Furthermore, since a large shearing stress acts on the single crystalline substrate at the cutting, the part of the single crystalline substrate is often lost or a deep fractured layer is often formed at the cutting surface.
Moreover, for using the single crystalline substrate for the electronic/optical device, the minor polishing is essential to the substrate, so that it need many processing steps.
It is an object of the present invention to provide a new producing method of a single crystalline member in which a single crystalline member usable for a single crystalline substrate can be directly obtained without the above cutting process and polishing process.
To iron out the above problems, this invention relates to a method for producing a single crystalline member, comprising the steps of:
preparing a single crystalline substrate,
forming a seed crystal part on a surface of the single crystalline substrate, and
contacting the seed crystal part with a solution containing a given element in supersaturation,
whereby a single crystal containing the given element as a constituting element is selectively and epitaxially grown in the perpendicular direction to the surface of the single crystalline substrate from the seed crystal part and thereby, a single crystalline member is produced.
In this way, in this invention, the seed crystal part is formed on the surface of the single crystalline substrate and then, the single crystalline member is obtained through the selective epitaxial growth in the perpendicular direction from the seed crystal.
Thus, by appropriately selecting the size and shape of the seed crystal part, the cross sectional shape of the single crystal member to be obtained is determined. Then, by appropriately controlling the selective epitaxial growth in the perpendicular direction to the surface of the single crystalline substrate, the single crystalline member having a desired size and shape can be obtained.
According to the present invention, the single crystalline member having a desired size and shape can be obtained by only the selective epitaxial growth. Thus, since in employing such a single crystalline member for a single crystalline substrate, the single crystalline substrate having a desired size and shape can be directly obtained, the conventional cutting process and polishing process is not needed.
Thus, the problems such as the loss of the part of the single crystal and the formation of the fractured layer in cutting the single crystal can be avoided. Moreover, a complex machine is not needed and the producing process of the desired single crystalline member can be simplified.
Furthermore, in the producing method of the present invention, since the single crystalline member is obtained in the perpendicular direction to the surface of the substrate, even if dislocations exist in the substrate, most of the dislocations go out from the single crystalline member. Thus, the single crystalline member has little dislocations, and then, becomes almost dislocation free.
Consequently, the single crystalline member having an excellent crystallinity can be obtained without the influence of the crystallinity of the single crystalline substrate.